Serum urate and the renal handling of urate were measured in 37 patients with primary hyperparathyroidism and in normal sex- and age-matched subjects. Serum urate was increased in the hyperparathyroid group compared to the control group (6.23 +/- 1.46 versus 4.64 +/- 1.24 mg/100 ml; p less than 0.005), whereas the fractional excretion of urate was decreased in hyperparathyroid patients compared to the controls (6.80 +/- 2.69 versus 8.73 +/- 3.47%; p less than 0.005). Twenty-four of these hyperparathyroid patients were studied 6 months after surgical correction of their disease. Serum urate decreased after surgery (5.14 +/- 1.65 mg/100 ml) compared to the preoperative state (5.92 +/- 1.46 mg/100 ml) and was no longer different from the normal values. The possible mechanisms of hyperuricemia associated with the hyperparathyroid state are discussed.